Pulsed laser printing

ABSTRACT

The present disclosure includes systems and techniques relating to pulse laser printing. In general, in one implementation, an apparatus includes: a laser operable to produce a pulsed printing beam; an optics assembly operable to focus and direct the pulsed printing beam; and electronics communicatively coupled with the laser and the optics assembly, the electronics being operable to control the laser and the optics assembly to generate power pulses of the pulsed printing beam in synchronization with a series of moves that steer the pulsed printing beam in a non-raster scanning pattern to predefined locations on a material to alter an optical characteristic of the material at the predefined locations, which are arranged to form at least a portion of a symbol. The electronics may deliver the power pulses in synchronization with arrival at the predefined locations, and the electronics may be configured to receive sensed feedback in a closed loop.

BACKGROUND

The present application describes systems and techniques relating tolaser printing systems, for example, laser-based systems for printingcodes on products.

Laser printing systems have been used to mark various types of surfaces.For example, laser printing has been used to mark codes on commerciallyavailable products. Such codes often include information correspondingto the time and place of product manufacture (e.g., a batch number).Typical types of codes marked on products include alphanumeric codes andmachine readable codes. When products are marked as part of amanufacturing or packaging process, increasing the speed of marking anddecreasing the costs of the printing system facilitate optimization ofthe manufacturing or packaging process.

SUMMARY

The present disclosure includes systems and techniques relating topulsed laser printing. According to an aspect, an apparatus includes alaser operable to produce a pulsed printing beam; an optics assemblyoperable to focus and direct the pulsed printing beam; and electronicscommunicatively coupled with the laser and the optics assembly, theelectronics being operable to control the laser and the optics assemblyto generate power pulses of the pulsed printing beam in synchronizationwith a series of moves that steer the pulsed printing beam in anon-raster scanning pattern to predefined locations on a material toalter an optical characteristic of the material at the predefinedlocations, which are arranged to form at least a portion of a symbol.The electronics can be operable to deliver the power pulses and initiatethe moves between the predefined locations at a common frequency duringformation of the symbol, and the common frequency can be a programmablecontrol variable of the electronics.

The electronics can be operable to deliver the power pulses insynchronization with arrival at the predefined locations. Theelectronics can be configured to receive feedback in a closed loop, thefeedback indicating arrival at the predefined locations, and use thefeedback to control timing of power pulse delivery. Furthermore, theelectronics can be configured to base the timing of power pulse deliveryat least in part on a recovery period of the laser and initiate themoves of the pulsed printing beam from the predefined locations duringdelivery of pulse-tail portions of the pulsed printing beam.

The electronics can be configured to receive sensed power delivery tothe predefined locations to control initiation of the moves between thepredefined locations. The electronics can include a mirror positionsensor and a laser emission sensor. Moreover, the electronics caninclude a laser controller operable to overdrive the laser and generatea superpulse beam.

The apparatus can include a continuously variable power supply operableto power the laser, and the electronics can be operable to control thecontinuously variable power supply to adjust a power output level of thelaser. The laser controller can be operable to overdrive the laser at afrequency above 1 kilohertz, and the power pulses can have rise and falltimes less than 50 microseconds. The laser can be an air cooled laser,and an average of power fluence during pulse delivery on the predefinedlocations can be greater than an average power of the laser whenoperated in a continuous wave mode. In addition, the laser controllercan provide two modes of operation, a superpulse mode and a continuouswave mode, and the electronics can select a mode of operation based on adensity of the predefined locations.

According to another aspect, a system includes a conveyor on which aproduct travels; a laser operable to produce a pulsed printing beam; anoptics assembly operable to focus and direct the pulsed printing beam;and electronics communicatively coupled with the laser and the opticsassembly, the electronics being operable to control the laser and theoptics assembly to generate power pulses of the pulsed printing beam insynchronization with a series of moves that steer the pulsed printingbeam in a non-raster scanning pattern to predefined locations on amaterial to alter an optical characteristic of the material at thepredefined locations, which are arranged to form at least a portion of asymbol, wherein the electronic overdrive the laser to generate asuperpulse beam, and the electronics deliver the power pulses insynchronization with arrival at the predefined locations.

According to another aspect, a technique includes directing a pulsedprinting beam through a series of moves that steer the pulsed printingbeam in a non-raster scanning pattern to predefined locations on amaterial to mark spots on the material at the predefined locations, thespots being arranged to form a symbol; and superpulsing a laser toproduce power pulses of the pulsed printing beam in synchronization withthe moves, such that delivery of the power pulses is synchronized witharrival at the predefined locations.

Feedback indicating arrival at the predefined locations can be receivedin a closed loop, and the feedback can be used to control timing ofpower pulse delivery. Sensed power delivery to the predefined locationscan be received and used to control initiation of the moves between thepredefined locations. A peak power of the pulsed printing beam can beadjusted using a continuously variable power supply. Moreover, selectionbetween superpulse and continuous wave modes of operation can be madebased on a density of the predefined locations.

One or more of the following advantages may be provided. The systems andtechniques described may result in reduced operating costs for a laserprinting system. A ten Watt laser printing system employing thetechniques described may be as effective as a traditional vector-basedfifty Watt laser printing system in a commercial laser marking process.The size of the laser printing system may be reduced. Electricity usagemay be decreased. Wasted energy may be reduced in spot-marking-basedlaser printing by decreasing the amount of energy deposited betweenspots making up the symbol(s) printed. More materials may be marked witha laser of a given power rating than would otherwise be possible.Products may be marked faster in a product line with a laser of a givenpower rating than would otherwise be possible. Laser coolingrequirements may be reduced, and overall efficiency may be improved.

Details of one or more implementations are set forth in the accompanyingdrawings and the description below. Other features and advantages may beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top, perspective view of a laser printing system.

FIG. 2 is a block diagram illustrating components of a laser printingdevice.

FIG. 3 illustrates example components of an optics assembly.

FIG. 4 illustrates an example symbol formed on a material of a product.

FIG. 5 illustrates multiple spots arranged so as to define a hexagonalpixel.

FIGS. 6 and 7 illustrates synchronization of power pulses with movesbetween predefined locations to mark spots on a material.

FIG. 8 is a block diagram illustrating components of a laser printingsystem.

FIG. 9 illustrates an example user interface screen for a laser printingsystem.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 is a top, perspective view of a laser printing system. The systemincludes a laser printing device 100 that generates a pulsed printingbeam 110, which is continuously directed through a series of movesbetween predefined locations on a material 170 to mark spots on thematerial at the predefined locations. The spots are arranged to form asymbol 180 on the material 170, and the power pulses of the pulsed laserbeam are synchronized with the moves. Details of this synchronization ofpower pulses with spot placement are described below in connection withFIGS. 6-8.

The diameter of a spot can vary depending on the implementation, butoften falls between 100 μm and 400 μm. The symbol 180 can be ahuman-readable symbol (e.g., an alpha-numeric character, such as the “T”shown), a machine-readable symbol (e.g., a one dimensional or twodimensional bar code), various other symbols (e.g., a symbolic image,such as a company logo or trademark), or combinations of these. Thematerial 170 can be part of a product 160 moving on a conveyor 150,which can be part of a manufacturing or packaging process.

A spot is formed on the product by altering a visible, opticalcharacteristic of the material 170 at the location where the pulsedprinting beam is incident on the material such that a mark is formedthat is visible to the naked human eye. The pulsed printing beam canalter a variety of optical characteristics. For instance, the pulsedprinting beam can cause one or more layers of material to be ablated sothe underlying layers are visible. Because upper layers of a materialused in packaging a product often have an ink layer on paper, removal ofthe ink layer leaves a spot where the paper is visible against thesurrounding ink layer. This can also be done when the ink layer residesbelow one or more additional layers, such as a wax layer over the inklayer. The refractive characteristics of a material can also be altered.For instance, the pulsed printing beam can be used to print informationon a plastic material, such as a soft drink bottle. The pulsed printingbeam alters the refractive characteristics of the plastic. The printedinformation is easily visible since the human eye can pick up thesections having contrasting refractive properties. Additionally, thepulsed printing beam can etch certain materials.

The predefined locations can be arranged such that the spots formmultiple symbols. The predefined locations can be arranged such that thespots form multiple pixels, and the pixels in turn form the one or moresymbols. Because the printing system employs a laser in order to printon the product, there is no need for consumables such as inks andsolvents. Accordingly, the printing system can reduce the costs andcomplexity associated with printing information on a product.

The products for use with the printing system can be products to be soldretail, products sold to businesses, or packaging of products. Examplesof products include pharmaceuticals, pharmaceutical packaging, foodpackaging, cosmetics, food such as eggs, dairy products, ice cream,computer components, automotive components, medical devices, detergentsand beverages such as soft drinks and wines. Moreover, the symbols canbe formed in multiple locations on a product and can include both codeinformation and image information.

The system includes electronics that operate the laser printing device100. These electronics can include analog and digital electroniccircuitry, such as one or more application specific integrated circuits(ASICs), as well as programmable electronics, such as one or moreprogrammable processors, and one or more memory devices. Theseelectronics are included in the laser printing device 100, but can alsobe included in one or more additional devices making up the laserprinting system. For example, a device 130 can be communicativelycoupled (by wire or wireless link) with the laser printing device 100.The device 130 can be an electronic user interface device designedspecifically for the laser printing device 100, a general purposecomputer programmed with user interface software, or a combination ofthese.

The user interface can be remote from the printing device 100, attachedto the printing device 100, and/or detachable from the printing device100. A suitable user interface can include an alphanumeric keyboard anda display. The user interface can be used to program the electronicsand/or set printing parameters. For instance, the user interface can beused to control the time that the pulsed printing beam 110 stays at alocation on the material 170 to form a spot, the size of any pixels usedto form a symbol, and the type and sequence of symbols that are formed.The user interface can also be used to manually activate the printingsystem. For instance, the user interface can include a print key thatcauses the laser printing device 100 to print on the material 170.

The laser printing system can be used to print symbols on products thatare moving, where there is a limited amount of time available forprinting on each product. The laser printing system can includeelectronics for varying the amount of time required to print the symbolson the product. For example, the laser printing system can includeelectronics for changing the density of pixels in the symbol(s) to beformed, such as by changing the density of individual pixels that definean alpha-numeric code or changing the number of pixels making up animage. Symbols having a reduced pixel density can be printed morequickly than symbols with an increased pixel density. Furthermore, theprinting system can include electronics for changing the size of thepixels. Smaller pixels require less printing time. The ability to changethe time required to print a symbol allows the printing system to beused in conjunction with an increased number of production lines.

The electronics that operate the laser printing device 100 can also bein communication with one or more sensors 140. These sensors can providethe electronics with information about the products on which theprinting system is to print. For instance, the sensors 140 can indicatethe location of a product relative to the printing system, the directionthat a product is moving and when a moving product has been stopped andwhen a product is in the correct position to be printed upon. Suitablesensors 140 include, but are not limited to, a speed sensor fordetecting the speed and/or direction that a product is moving, and alocation sensor for indicating when a product is positioned in front ofthe sensor.

The laser printing system can operate as part of a product line and canprint on a moving product or a stationary product. A product line cantemporarily stop the product 160 in front of the laser printing device100. A sensor 140 can be a device that triggers the printing (e.g., adevice that produces a light beam, which is disrupted by the product)either immediately or after a time delay. When the printing systemoperates on a moving product, the electronics can use signals from aspeed sensor 140 to determine the speed and direction of the product 160on the product line. Suitable speed sensors include, but are not limitedto, encoders and resolvers. The printing system can determine the speedof the product 160 on the line and use this speed to determine a symbolposition time delay. The symbol position time delay is determined suchthat the symbol is printed at a desired position on the product 160. Thesymbols are then printed as the product 160 moves past the printingdevice 100 based on the determined symbol position time delay.Additionally, the printing system can determine the speed of a nextproduct while printing on a current product.

When setting up the laser printing system, the distance between thelaser printing device 100 and the product 160 and/or the sensor 140 canbe administratively entered into the electronics with the userinterface. Alternatively, the sensor 140 can be attached to the laserprinting device 100 so as to provide a fixed and known distance betweenthe sensor 140 and the pulsed printing beam 110. In this latterembodiment, the distance is known to the electronics in the system anddoes not need to be administratively entered.

The laser printing device 100 can include a printing beam exit member120 through which the pulsed printing beam 110 exits a housing of theprinting device 100. The printing beam exit member 120 can be an openingin the housing or an immobile window mounted in the housing. In anotherembodiment, the printing beam exit member 120 can be moved relative tothe housing as illustrated by the arrows labeled A. In this embodiment,the printing beam exit member 120 can be rotatably moved (e.g., manuallyadjusted) through a continuous set of multiple directional positions topoint the pulsed printing beam 110 toward a particular position on thematerial 170, thus allowing the pulsed printing beam 110 to be readilyaimed, after the device 100 has been installed, by manipulating theprinting beam exit member 120.

The laser printing device 100 can include components for defining aprint zone on the material 170. For example, a rectangle can beprojected onto the material 170, where the one or more symbols will beformed within the print zone. During operation of the laser printingsystem, the print zone can be formed on the material 170; an operatorcan adjust the beam exit member 120 so that the print zone appears atthe desired location on the material 170. A user interface can then beused to activate printing within the print zone. Thus, the operator ofthe printing system can select where the printing beam prints on thematerial 160 by ensuring that the print zone appears in the desiredprint location. Other suitable print zone marks include, but are notlimited to, marks at the four corners of a print zone, a mark positionedin the center of the print zone, and a dashed line around the printzone.

Additionally, the electronics of the laser printing system can bedesigned to control the size and geometry of the print zone. As aresult, the electronics can match the size and shape of the symbols tobe printed on the material 170. For example, when an unusually largecode is to be printed on the material 170, the electronics can enlargethe print zone so the code will be formed entirely within the printzone. As a result, an increase in the size of the code will not resultin erroneous positioning of the code on the material 170.

FIG. 2 is a block diagram illustrating components of the laser printingdevice 100. A laser 210 produces the pulsed printing beam. For example,the laser 210 can be operated in a superpulse mode. By using superpulse,a higher peak power output can be obtained than the average power outputof the laser when run in a normal operational mode. Various differenttypes of lasers can be used, and in particular, a lower power laser canbe used (lower power relative to what would normally be needed to markthe material) due to the effective increase in delivered power createdby the systems and techniques described here. For example, the laser 210can be a CO₂ air cooled laser. In various embodiments, the laser can bea 30 Watt laser, a 20 Watt laser, a 10 Watt laser or a 5 Watt laser.When the laser is a low power laser, the components of the laserprinting device 100 can be mounted in a housing having a size on theorder of an ink jet printer (e.g., a volume of less than 1500 cubicinches).

To make the laser 210 operable in a superpulse mode, more gas may beused than would be the case for a similar laser that only operates in acontinuous wave mode, and the gas percentages can be adjusted as needed,based on the superpulse frequencies to be obtained. In addition, moreadvanced dirver(s) can also contribute to making the laser 210 operablein a superpulse mode. In general, there is a balance to be found, whichis dependent on the internal laser geometry. Thus, the laser 210 can bemade to operate in a superpulse mode by adjusting gas percentages anddensity, driver component(s) and laser geometry.

The pulsed printing beam passes through an optics assembly 220, whichsteers the pulsed printing beam from one location to another location onthe material. The optics assembly 220 includes components for alteringthe direction of the pulsed printing beam. These components can becontrolled to steer the pulsed printing beam from one location toanother location in an non-raster scanning pattern (i.e., a scanningpattern other than one of parallel lines) so as to create a spot at eachof the locations.

Electronics 230 are in communication with the laser 210 and the opticsassembly 220. The electronics 230 can control the operation of the laser210 and the optics assembly 220. The electronics 230 can control theoptics assembly 220 to adjust the direction of the pulsed printing beam,the length of time that the pulsed printing beam remains at a locationon the material where a spot is to be formed, the speed that the pulsedprinting beam moves between locations where the beam dwells, the size ofpixels used to create symbols, and the selection of symbols created.Moreover, the electronics 230 control the laser 210 to generate thepower pulses of the pulsed printing beam in synchronization with themoves of the pulsed printing beam between locations where the beamdwells. The dwell time used and the power profile of the pulsed printingbeam generated can be adjusted based in part on the nature of thematerial to be marked.

The laser printing device 100 can include a continuously variable powersupply 240. The electronics 230 can control the continuously variablepower supply to adjust a power output level of the laser. For example,the power supply 240, which powers the laser 210, can be run frombetween 30 and 50 Watts. The laser 210 can be run in a continuous wave(CW) mode at about 32 Watts, and the laser 210 can be run in asuperpulse mode at about 48 Watts. Moreover, the superpulse peak powercan be adjusted, at least in part, by controlling the variable powersupply. The pulse width can also be adjusted, and both pulse width andpower supply can be adjusted in order to tune the power and the fluencewith the moves.

FIG. 3 illustrates example components of the optics assembly 220 inrelation to a housing 16 of the laser printing device 100. The opticsassembly 220 includes a laser source 12 that provides the pulsedprinting beam 110. The beam 110 passes through a first negative lens 50,which expands the printing beam 110. The optics assembly 220 alsoincludes a print zone light source 52 for producing a print zone beam53. The print zone beam 53 passes through a second negative lens 54,which expands the print zone beam.

Although the printing beam 110 and the print zone beam 53 areillustrated as being concurrently produced, the electronics can causethem to be produced independent of one another (e.g., the print zonebeam 53 can be activated whenever the printing beam 110 is deactivatedand visa versa). Further, the print zone beam 53 is optional and neednot be included in the optics assembly 220. The printing beam 110 andthe print zone beam 53 are combined at a beam combiner 56. The combinedbeams pass through a positive lens 58, which collimates the beams beforethey are turned at a reflector 60. The combined beams then pass to aplurality of mirrors 62, which reflect the combined beams toward asecond positive lens 63, which focuses the combined beams. The combinedbeams then pass through a protective window 64 before passing to thematerial 170.

The mirrors 62 can be two mirrors arranged such that the first mirrorreflects the beam 110 onto the second mirror (in a direction parallelwith a line coming out of the page), and the second mirror reflects thebeam 110 toward the second positive lens 63. One or more of the mirrors62 can be coupled with one or more actuators 70 that move the mirror(s)62. Suitable actuators 70 include, but are not limited to, micromotors.The actuators 70 are controlled by the electronics. The electronics canuse the actuators 70 to steer the printing beam 110 to form thesymbol(s) on the material 170, and the electronics can use the actuators70 to steer the print zone beam 53 to produce the print zone (e.g., theprint zone beam 53 can be steered to trace a rectangle around the printzone at a speed which causes the rectangle to appear solid to the humaneye or at about 100 cycles/second).

As discussed above, the laser printing system can include a printingbeam exit member 120 that can be moved relative to a device housing 16.A frame 76 supports the printing beam exit member 120 within the housing16. A bearing 78 positioned between the frame 76 and the printing beamexit member 120 allows the printing beam exit member 120 to moverelative to the frame 76 (i.e., the exit member 120 rotates into and outof the page). The printing beam 110 passes through the bearing 78 alongthe axis of rotation permitted by the bearing 78. Hence, movement of theprinting beam exit member 120 relative to the frame 76 does not changethe position of the printing beam 110 relative to the bearing 78.

The mirrors 62 and the actuators 70 are coupled with the printing beamexit member 120. As a result, the mirrors 62 and the actuators 70 movewith the printing beam exit member 120 as the printing beam exit member120 is moved relative to the housing 16. Further, a portion of a firstof the mirrors 62 is positioned along the bearing's axis of rotation.Hence, movement of the printing beam exit member 120 does not alter theangle of incidence between the printing beam 110 and the first mirror.Accordingly, the first mirror directs the printing beam 110 toward thesame portion of the second mirror and the printing beam 110 exits thehousing 16 through the same portion of the window when the printing beamexit member 120 is moved relative to the housing 16.

For additional details regarding the optics assembly 220 and techniquesfor laser printing on a moving product, see U.S. Pat. No. 6,791,592,issued Sep. 14, 2004, and entitled “Printing A Code on a Product”, whichis hereby incorporated by reference. Various other optics assemblies canalso be used. See for example, U.S. patent application Ser. No.10/693,356, filed Oct. 24, 2003, and entitled “Low Angle Optics andReversed Optics”, which is hereby incorporated by reference.

FIG. 4 illustrates an example symbol 180 formed on a material 170 of aproduct 160. The symbol 180 is formed of a set of pixels 410, and thedensity of pixels 410 (i.e., the number of pixels forming a symbol of agiven size) can be adjusted as needed, even to the point where thepixels overlap each other. Each pixel 410 can be a single spot ormultiple spots created by the pulsed laser beam. For example, each pixel410 can be three spots grouped together into a roughly triangular pixel.Some pixels 410 can have a different size than other pixels 410.Different shapes for pixels made up of multiple spots are possible aswell, such as square, hexagonal, or circular pixels.

Moreover, in some implementations, an operator of the printing systemcan use the user interface to select the size and shape of the pixels.FIG. 5 illustrates multiple spots 510 arranged so as to define ahexagonal pixel 500. Moving the printing beam from one location toanother location, as illustrated by the arrow labeled A, creates thepixel 500 by creating a spot 510 at each location.

The time required to form a spot is generally a function of thecomponents of the material. For instance, the material may have an inklayer and an overlying layer (e.g., a wax layer that protects thepackaging and gives it an attractive appearance), and the time needed toablate the wax layer and the ink layer can be about 35 microseconds to 1millisecond using the air cooled lasers described herein.

The distance between the spots and/or pixels can be adjusted to increaseor decrease the size and/or density of the symbol. In some instances,the distance between the pixels is reduced to the point that theperimeter of one pixel abuts the perimeter of another pixel. When thepixel perimeters abut one another, a code and/or an image being printedcan have a solid and continuous appearance.

The size of the pixels formed by the printing system can be adjusted byincreasing the number of spots used to create the pixel and/or bydecreasing the density of spots while keeping the number of spots thesame. When faster printing is needed, the total number of spots used tomake up the symbol can be decreased, such as by decreasing the densityof spots used to make up a symbol of a given size. This adjustmentcapability can also be made available to the operator of the of theprinting system through the user interface. Moreover, the printingsystem electronics can be configured to select a mode of operation (CWor superpulse) based on a density of the spots in the code.

The electronics can include components that facilitate input of symbols.The electronics can include a database that associates alpha-numericsymbols with particular pixel patterns. As a result, the operator canenter a symbol or symbol sequence into the user interface, and theprinting system consults the database to determine the pixel patternassociated with each symbol. The electronics can also include an inputinterface for bar code information and image information. For example, asoftware application can be used to enter two dimensional bar codeinformation, which can be converted into a set of character informationin a font specified for 2D bar code printing. Such character informationcan be communicated to the laser printing device, which can includeelectronics that recognize the font and can thus convert the characterinformation into the pixel pattern (e.g., each “character” in therecognized font can correspond to a vertical set of elements in the 2Dbar code). The software application can also be used to enter a graphicimage, which can be converted into the pixel pattern for printing, byfilling dark areas of the image to be marked with concentric outlines ofpixels (e.g., single spot pixels), starting at the perimeter and movingin to the center of the image until all dark areas are filled.

The electronics can use the pixel pattern of each symbol to form a firstdata set which indicates the position of each pixel. For instance, eachpixel can be associated with a Cartesian coordinate, which indicateswhere the pixels are to be printed relative to one another. Othercoordinate systems and methods can also be used to control the relativepositioning of the pixels in a symbol.

FIG. 6 illustrates synchronization of power pulses with moves betweenpredefined locations to mark spots on a material. The predefinedlocations correspond to where the spots are to be placed and can bespecified according to a corrected data set for a moving product. Agraph 600 shows moves, M1-M6, and power pulses, P0-P5. The x axis of thegraph 600 indicates time, the upper half of the y axis indicates thevelocity of the pulsed printing beam across the material, and the lowerhalf of the y axis indicates the power level of the pulsed printing beam(moving downward in the lower half of the graph 600 indicates increasingpower). A move between the predefined locations can be accomplished bymoving one or more mirrors 62 in the optics assembly 220. This caninvolve rapidly accelerating to the top speed (at time T1 for move M1),cruising at that top speed, and then rapidly decelerating to a stop atthe next predefined location (at time T2 for move M1), as illustrated inFIG. 6.

The power pulses, P0-P5, of the pulsed printing beam can have a powerdistribution as illustrated and can be delivered at a common frequencywith initiation of the moves, M1-M6, between the predefined locations.Delivery of the power pulses can be represented by the initiation of thepower pulses, and thus the time between T0 and T3 (the time betweeninitiation of pulse P0 and pulse P1) will be generally equal to the timebetween T1 and T4 (the time between initiation of move M1 and move M2).Additionally, the pulsed printing beam can be held on the predefinedlocations during delivery of pulse-peak portions of the pulsed printingbeam, and moves of the pulsed printing beam can be initiated duringdelivery of pulse-tail portions of the pulsed printing beam, as shown.Thus, move M1 begins at time T1 during delivery of the pulse-tailportion of pulse P0, move M2 begins at time T4 during delivery of thepulse-tail portion of the pulse P1, and the pulse-tail portion of P1ends during move M2 at time T5. Moreover, a move may be so short as tooccur entirely within the pulse-tail portion, as illustrated by moves M3and M5. The reduced power of the beam during this pulse-tail, and thespeed with which the beam moves over the material results in no visiblemarking during these moves.

The common frequency of the moves and the pulses can be determinedaccording to a maximum time needed for a move. This maximum time can bepreset based on the capabilities of the laser printing system (e.g.,based on the time need to make a largest possible move available with agiven optical assembly design), or this maximum time can be set on thefly based on the capabilities of the laser printing system and thesymbol(s) to be printed (e.g., based on a maximum move time needed for agiven corrected data set). In the graph 600, the move M4 is a maximummove, and the pulse P4 is initiated when the pulsed printing beam beginsits deceleration.

The common frequency of the moves and the pulses can also be determinedaccording to how fast the laser can be pulsed, which depends on thelaser and driver design, including a recovery period of the pulsed laser(e.g., a gas recovery time of a superpulsed laser). The upper limit onpulse speed for the laser generally sets the upper limit on the commonfrequency. Using the pulse speed to set the common frequency can be inaddition to using the maximum move time, or the pulse speed alone can beused in some implementations. For example, in some instances, all movesare so fast that the common frequency is set according the maximumpulsing frequency available in light of a given material to be marked.

The synchronization of power pulses with moves illustrated in FIG. 6 canbe implemented in an open-loop control system. When delivery of thepower pulses and initiation of the moves are both controlled using acommon frequency, the electronics need not include sensor feedback toconfirm arrival at the next predefined location before making the spot.Arrival at the next predefined location within the allotted time can beassumed given a properly set common frequency. In some implementations,the moves can take times between 5 microseconds and 1 millisecond,depending on the driver(s), power supply and distance moved. The dwelltime at each location (e.g., time T3 to time T4) can be between 20 and100 microseconds, and the energy delivered during the dwell time can bebetween 0.05 and 2 Joules.

FIG. 7 also illustrates synchronization of power pulses with movesbetween predefined locations to mark spots on a material. A graph 700shows moves, M1-M6, and power pulses, P1-P5, with the same axes as inthe graph 600. In this case, the timing of delivery of the power pulsesis based on the timing of arrival of the pulsed printing beam at thepredefined locations. For example, the timing can be such that the powerpulse reaches 70-80% of it peak power at the same time that the mirrorsare 95-100% settled at the next location for spot placement.Additionally, the timing of delivery of the power pulses can be furtherbased on a recovery period of the pulsed laser when this recovery periodexceeds the time needed for the current move. However, in someimplementations, the power pulse need not reach zero before the nextpulse begins.

As before, the pulsed printing beam can be held on the predefinedlocations during delivery of pulse-peak portions of the pulsed printingbeam, and moves of the pulsed printing beam can be initiated duringdelivery of pulse-tail portions of the pulsed printing beam. Thepulse-peak portions of the pulsed laser beam deliver greater power in ashort amount of time than possible for the same laser operated in acontinuous wave mode. A line 710 indicates the power output of the laserwhen operated in a continuous wave mode; a line 720 indicates theaverage power output of the same laser operated in a pulsed mode; and aline 730 indicates the average power output, during formation of thespot, of the same laser operated in the pulsed mode. Thus, a laser witha given power rating can have a greater effective power when powerpulses of the laser are synchronized with the spot-mark placement asdescribed. For example, spots on a given material can be formed morerapidly, and spots can be efficiently formed on materials that are lesssusceptible to laser ablation, than would be possible with the samelaser operated in a continuous wave mode.

Additionally, the moves can be at times much closer together thanillustrated. For example, the printing beam may in fact never fullystop, but rather slow down over the predefined location, at which pointthe laser pulse is delivered. Thus, the dwell time during which a powerpulse forms a spot may be a time of relatively slow laser movement asopposed to a full stop of the laser over the formed spot.

The synchronization of power pulses with moves illustrated in FIG. 7 canbe implemented in an open-loop control system or a closed-loop controlsystem. In an open-loop implementation, the electronics of the printingsystem can determine the time needed for the various moves M1-M6 basedon the spot-placement information for a given set of one or more symbolsto be printed, and the time between pulses can be set accordingly. In aclosed-loop implementation, the electronics can sense the timing ofarrival at the predefined locations to control the timing of delivery ofthe power pulses. Additionally, in a closed-loop implementation, theelectronics can sense power delivery to the predefined locations todetermine when the spot has been formed due to delivery of enoughenergy, and to control initiation of the moves between the predefinedlocations.

FIG. 8 is a block diagram illustrating components of a laser printingsystem. This printing system has a closed-loop control system in whichone or more sensors 800 provide feedback to a controller 830. Thecontroller 830 overdrives a laser 810 to generate a superpulsed printingbeam with pulses occurring at times determined based on the informationprovided by the sensor(s) 800. A higher source voltage is provided tothe laser 810, such that when the laser 810 is turned on, a power spikeis produced. The controller 830 can be operable to overdrive the laser810 at frequencies at or above 1 kilohertz, 5 kilohertz, 7.5 kilohertz,10 kilohertz or 20 kilohertz. The laser 810 can be an air cooled laser,such as a CO₂ laser of 25 Watts or less, 15 Watts or less, or 8 Watts orless.

Additionally, the controller 830 directs optics 820 to move the pulsedlaser beam at times determined based on the information provided by thesensor(s) 800. The sensor(s) 800 can be built into the optics 820. Thesensor(s) 800 can include a mirror position sensor used to verifyarrival of the pulsed printing beam at the predefined locations. Themirror position sensor can employ any of various commercially availablesensor technologies, such as resistance, magnetic, or transducer-basedsensors. The sensor(s) 800 can also include a laser emission sensor usedto identify the end of the pulse-peak portions of the pulsed printingbeam. The laser emission sensor can measure various aspects of the laserto determine the emission level, such as by measuring the power in line(e.g. an in-line beam splitter with a germanium sensor), measuring anenergy halo created by sending the beam through an aperture, measuringcurrent draw, measuring voltage level, measuring the drive input to thelaser, or various other direct or indirect methods of determining wherethe laser is in the known power profile of the pulses. The controller830 can initiate the laser pulses based on the information provided bythe mirror position sensor and can initiate moves of the pulsed printingbeam based on the information provided by the laser emission sensor.Using such sensors allows verification of arrival at the predefinedlocations and verification that enough energy content above the lazingthreshold of the substrate has been deposited to make the spot.

The controller 830 can be part of the electronics described above inconnection with FIGS. 1 and 2. FIG. 8 can also illustrate an open-loopimplementation by disregarding the sensor(s) 800. Moreover, thecontroller 830 can provide two modes of laser operation, a superpulsemode and a continuous wave mode, and two modes of synchronization, thecommon frequency mode and the fire-upon-arrival mode described above.

FIG. 9 illustrates an example user interface screen 900 for a laserprinting system. The user interface screen 900 includes a set frequencybutton 910, which can be used to place the system in the commonfrequency mode of operation. The common frequency can be specifiedautomatically by the system or specified by a system operator throughthe user interface. Thus, the common frequency can be a programmablecontrol variable of the electronics.

The user interface screen 900 includes a superpulse mode button 920,which can be used to place the system in the superpulse mode ofoperation. The user interface screen 900 includes a continuous wave modebutton 930, which can be used to place the system in the continuous wavemode of operation. Additionally, the user interface screen 900 includesa smart mode select button 940, which can be used to instruct the systemto select a mode of operation based on a density of the spots in the oneor more symbols to be formed. For example, if the moves between spotsare all very short, the system can determine that the continuous wavemode of operation is optimal for the given symbol(s) to be printed on aproduct, and if the moves between spots are relatively larger, thesystem can determine that the superpulse mode of operation is optimalfor the given symbol(s).

The functional operations described in this specification can beimplemented in digital electronic circuitry, or in computer hardware,firmware, software, or in combinations of them, such as the structuralmeans disclosed in this specification and structural equivalentsthereof. The described processing operations can be performed by aprogrammable processor executing a program of instructions to performfunctions by operating on input data and generating output. Suitableprocessors include, by way of example, both general and special purposemicroprocessors. Generally, a processor will receive instructions anddata from a read-only memory, a random access memory and/or amachine-readable signal (e.g., a digital signal received through anetwork connection). Storage devices suitable for tangibly embodyingsoftware program instructions and data include all forms of non-volatilememory, including by way of example semiconductor memory devices, suchas EPROM (electrically programmable read-only memory), EEPROM(electrically erasable programmable read-only memory), and flash memorydevices; magnetic disks such as internal hard disks and removable disks;magneto-optical disks; and optical disks, such as CD-ROM disks. Any ofthe foregoing can be supplemented by, or incorporated in, ASICs.

To provide for interaction with a user, the systems and techniquesdescribed can be implemented on a data processing system having adisplay device such as a monitor or LCD (liquid crystal display) screenfor displaying information to the user and a keyboard and a pointingdevice such as a mouse or a trackball by which the user can provideinput to the computer system. The data processing system can beprogrammed to provide a graphical user interface through which programsinteract with users.

Various embodiments have been described above. Other embodiments arewithin the scope of the following claims. For example, the electronicscan include a digital signal processor (DSP) used with the motordriver(s), and instead of a superpulsed laser, a Q-switched laser can beused.

1. An apparatus comprising: a laser operable to produce a pulsedprinting beam; an optics assembly operable to focus and direct thepulsed printing beam; and electronics communicatively coupled with thelaser and the optics assembly, the electronics being operable to controlthe laser and the optics assembly to generate power pulses of the pulsedprinting beam in synchronization with a series of moves that steer thepulsed printing beam in a non-raster scanning pattern to predefinedlocations on a material to alter an optical characteristic of thematerial at the predefined locations, which are arranged to form atleast a portion of a symbol; wherein the electronics are operable todeliver the power pulses in synchronization with arrival at thepredefined locations; wherein the electronics are configured to receivefeedback in a closed loop, the feedback indicating arrival at thepredefined locations, and use the feedback to control timing of powerpulse delivery; and wherein the electronics are further configured tobase the timing of power pulse delivery at least in part on a recoveryperiod of the laser and initiate the moves of the pulsed printing beamfrom the predefined locations during delivery of pulse-tail portions ofthe pulsed printing beam.
 2. The apparatus of claim 1, furthercomprising a continuously variable power supply operable to power thelaser, and wherein the electronics are operable to control thecontinuously variable power supply to adjust a power output level of thelaser.
 3. An apparatus comprising: a laser operable to produce a pulsedprinting beam; an optics assembly operable to focus and direct thepulsed printing beam; and electronics communicatively coupled with thelaser and the optics assembly, the electronics being operable to controlthe laser and the optics assembly to generate power pulses of the pulsedprinting beam in synchronization with a series of moves that steer thepulsed printing beam in a non-raster scanning pattern to predefinedlocations on a material to alter an optical characteristic of thematerial at the predefined locations, which are arranged to form atleast a portion of a symbol; wherein the electronics are operable todeliver the power pulses in synchronization with arrival at thepredefined locations; wherein the electronics are configured to receivefeedback in a closed loop, the feedback indicating arrival at thepredefined locations, and use the feedback to control timing of powerpulse delivery; and wherein the electronics are configured to receivesensed power delivery to the predefined locations to control initiationof the moves between the predefined locations.
 4. The apparatus of claim3, wherein the electronics comprise a mirror position sensor and a laseremission sensor.
 5. An apparatus comprising: a laser operable to producea pulsed printing beam; an optics assembly operable to focus and directthe pulsed printing beam; and electronics communicatively coupled withthe laser and the optics assembly, the electronics being operable tocontrol the laser and the optics assembly to generate power pulses ofthe pulsed printing beam in synchronization with a series of moves thatsteer the pulsed printing beam in a non-raster scanning pattern topredefined locations on a material to alter an optical characteristic ofthe material at the predefined locations, which are arranged to form atleast a portion of a symbol; wherein the electronics comprise a lasercontroller operable to overdrive the laser and generate the pulsedprinting beam comprising a superpulse beam; wherein the laser controllerprovides two modes of operation, a superpulse mode and a continuous wavemode, and the electronics select a mode of operation based on a densityof the predefined locations; and wherein the laser controller isoperable to overdrive the laser at a frequency above 1 kilohertz, andthe power pulses have rise and fall times less than 50 microseconds. 6.The apparatus of claim 5, wherein the laser comprises an air cooledlaser, and an average of power fluence during pulse delivery on thepredefined locations is greater than an average power of the laser whenoperated in a continuous wave mode.
 7. A system comprising: a conveyoron which a product travels; a laser operable to produce a pulsedprinting beam; an optics assembly operable to focus and direct thepulsed printing beam; and electronics communicatively coupled with thelaser and the optics assembly, the electronics being operable to controlthe laser and the optics assembly to generate power pulses of the pulsedprinting beam in synchronization with a series of moves that steer thepulsed printing beam in a non-raster scanning pattern to predefinedlocations on a material to alter an optical characteristic of thematerial at the predefined locations, which are arranged to form atleast a portion of a symbol, wherein the electronic overdrive the laserto generate the pulsed printing beam comprising a superpulse beam, andthe electronics deliver the power pulses in synchronization with arrivalat the predefined locations; wherein the electronics are configured toreceive sensed power delivery to the predefined locations to controlinitiation of the moves between the predefined locations.
 8. The systemof claim 7, wherein the electronics are configured to receive feedbackin a closed loop, the feedback indicating arrival at the predefinedlocations, and use the feedback to control timing of power pulsedelivery.
 9. The system of claim 7, further comprising a continuouslyvariable power supply operable to power the laser, and wherein theelectronics are operable to control the continuously variable powersupply to adjust a power output level of the laser.
 10. The system ofclaim 7, wherein the laser controller is operable to overdrive the laserat a frequency above 5 kilohertz, and the power pulses have rise andfall times less than 40 microseconds.
 11. The system of claim 7, whereinthe laser controller provides two modes of operation, a superpulse modeand a continuous wave mode, and the electronics select a mode ofoperation based on a density of the predefined locations.
 12. A methodcomprising: directing a pulsed printing beam through a series of movesthat steer the pulsed printing beam in a non-raster scanning pattern topredefined locations on a material to mark spots on the material at thepredefined locations, the spots being arranged to form a symbol;superpulsing a laser to produce power pulses of the pulsed printing beamin synchronization with the moves, such that delivery of the powerpulses is synchronized with arrival at the predefined locations; andreceiving sensed power delivery to the predefined locations to controlinitiation of the moves between the predefined locations.
 13. The methodof claim 12, further comprising receiving feedback in a closed loop, thefeedback indicating arrival at the predefined locations, and using thefeedback to control timing of power pulse delivery.
 14. The method ofclaim 12, further comprising adjusting a peak power of the pulsedprinting beam using a continuously variable power supply.
 15. The methodof claim 12, further comprising selecting between superpulse andcontinuous wave modes of operation based on a density of the predefinedlocations.